According to LCD devices, alignment of LC molecules is controlled by an electric field formed between electrodes, thereby adjusting ON and OFF of LC display. Reflective, transmissive, and transmissive LCD devices are mentioned as the LCD devices.
Under relatively dark environments such as indoor environment, transmissive LCD devices using light from a light source such as a backlight are usually adopted. Under relatively bright environments such as outdoor environment, reflective LCD devices using ambient light are usually adopted. Transflective LCD devices can provide mainly transmission display under indoor environments and mainly reflection display under outdoor environments. So such transflective LCD devices can provide high quality display under any environments, both indoor and outdoor environments. Now such transflective LCD devices are installed in various mobile equipment such as a cellular phone, a PDA, and a digital camera. According to the transflective LCD devices, paths of display light are different between a transmission region and a reflection region. In reflection display, ambient light having passed through a reflection region of a LC layer is reflected by a reflection member and then passes through that region again. So light having passed through the LC layer twice is used for reflection display. In contrast, in transmission display, light having passed through a transmission region of the LC layer once is used for transmission display. So if the thickness of the LC layer is uniform between the transmission region and the reflection region, a retardation for light having passed through the LC layer is different between the two regions, failing to provide proper display. The thickness of the LC layer (cell gap) between the transmission region and the reflection region needs to be optimized for proper display. Typically, the LC layer is so designed that the thickness thereof in the transmission region is twice larger than that in the reflection region because the reflection light actually passes through the LC layer with a thickness twice larger than that of the LC layer through which the transmission light passes.
VA (vertical alignment) or IPS (in-plane switching) LCD devices are used as the LCD devices, for example. According to VA LCD devices, an electrode for controlling alignment of LC molecules is arranged on both substrates with a LC layer therebetween, and under no voltage application, the LC molecules are vertically aligned to the substrate surfaces. By applying a threshold voltage or higher between the both electrodes, the LC molecules are aligned in parallel to the substrate surfaces. According to IPS LCD devices, an electrode for controlling alignment of LC molecules is arranged on either one of a pair of substrates, and under no voltage application, the LC molecules are aligned in parallel to the substrate surfaces. By applying a threshold voltage or higher between the both electrodes, the LC molecules are aligned in parallel to the substrate surfaces in an in-plane direction. VA LCD devices are known to provide high contrast display. IPS LCD devices are known to provide wide viewing angle display.
LCD devices that provide reflection display need to have at least one λ/4 retarder in the reflection region together with a polarizer. This is because in reflection display, linearly-polarized light needs to be converted into circularly-polarized light, in principle. By arranging a λ/4 retarder together with a polarizer, linearly-polarized light having passed through the polarizer can be converted into circularly-polarized light. For example, Patent Document 1 discloses the following IPS LCD device including a λ/4 retarder. The λ/4 retarder is selectively arranged corresponding to a reflection layer, and a multi-gap structure is formed in order that a LC layer in a reflection region has a thickness smaller than a thickness of the LC layer in a transmission region.
According to VA LCD devices, MVA (multi-domain vertical alignment) LCD devices are now increasingly used because such devices are effective in increase in viewing angle and contrast ratio. VA LCD devices provide display by applying a voltage to a LC layer to tilt LC molecules, which are vertically aligned to substrate surfaces under no voltage application. MVA LCD devices provide wide viewing angle and high contrast display by tilting LC molecules toward a projection formed on surfaces facing a LC layer of substrates.
MVA transflective LCD devices also need to include a λ/4 retarder. The transflective LCD devices have a transmission region together with a reflection region. In the transmission region, another λ/4 retarder needs to be arranged, together with the λ/4 retarder arranged in the reflection region. However, a difference in parameter between such two different λ/4 retarders possibly leads to a reduction in contrast ratio of transmission display. In view of this, for example, Patent Document 2 discloses an LCD device with a multi-gap structure provided by arranging a retardation layer only in a reflection region, thereby creating a difference in LC layer thickness between the transmission region and the reflection region. According to the LCD device of Patent Document 2, projections (hereinafter, also referred to as a “rivet”) are arranged in a dotted pattern when viewed from a display face to control LC molecules. Thus, this LCD device can provide wide viewing angle display.
Such LCD devices are now being rapidly developed. A further improvement in display qualities are strongly needed for MVA LCD devices.
[Patent Document 1]
    Japanese Kokai Publication No. 2006-71977[Patent Document 2]    WO 2007/063629